The overall goals are (a) to identify biochemical defense mechanisms that plants have evolved to help them cope with osmotic stress, (b) to define and isolate the enzymes involved, (c) to clone the corresponding genes, and (d) to use these genes to metabolically engineer improved crop stress resistance. Our research focuses on betaines and their sulfonium analogs, which are potent osmoprotectants and cryoprotectants. These compounds and their biosynthetic intermediates are highly amenable to mass spectral analysis. Specific objectives are (i) to use cloned plant genes for glycine betaine synthesis to engineer glycine betaine accumulation (supported by USDA-NRI-CRGP); (ii) to identify the biosynthetic pathways of DMSP and related compounds in higher plants and in marine algae, and to isolate their enzymes and genes.